WSAStartUP错误.

Question

procedure TForm1.BitBtn2Click(Sender: TObject);
var
    WSAData:TWSAData;
    Err,ipaddress:dword;
    hos:phostent;
begin
      try
         WSAStartup($101,WSAData);//单步执行到此出错
      except
        Err:=WSAGetLastError;
        ShowMessage(IntToStr(Err));
        WSACleanup;
      end;
      ipaddress:=inet_addr(PChar(PingEdit.text));
      hos:=gethostbyaddr(@ipaddress,sizeof(ipaddress),PF_INET);
      Label3.Caption:=hos.h_name;
      WSACleanup;
end;  wVersionRequested:=MakeWord(1,1);
  nSockErr:=WSAStartup(wVersionRequested,WSAData);//);//单步执行到此也要报错.---------------------------
Debugger Exception Notification
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Project Project1.exe raised exception class EAccessViolation with message 'Access violation at address 00000000. Read of address 00000000'. Process stopped. Use Step or Run to continue.
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OK   Help   
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我的系统环境:delphi6+Winxp sp2